Apparatus for generating a two-dimensional coloured display

Abstract

Apparatus for generating a two-dimensional coloured display in which there is a variation of colour across the display in a predetermined manner, the colour of each pixel in the display being defined by one or more colour components. The apparatus comprises, for each colour component, a memory for storing a pair of gradation curves (X(i), Y(i)) representing the variation in intensity of the color component in orthogonal directions X, Y across the display; a monitor; and processing apparatus. The processing apparatus determines a resultant colour component value V(i,j) for a pixel to be displayed at a location (i,j) on the monitor in accordance with the following formula: V(i,j)=f[a(X(i))b(Y(j))+c(X(i))d(Y(j))] where the pixel has coordinates i,j and k is a normalizing constant, and where a, c, are functions of X(i), b, d are functions of Y(j) and f is an output function, the functions being chosen such that V(i,j) exhibits no discontinuities for all values of X(i), Y(j). The monitor is responsive to the resultant colour component values V(i,j) to display a corresponding colour at a position in the display corresponding to that pixel.

I claim: 
     
       1. Apparatus for generating a two-dimensional coloured display in which there is a variation of colour across the display in a predetermined manner, the colour of each pixel in the display being defined by at least one colour components, the apparatus comprising, for each colour component, a memory for storing a pair of gradation curves (X(i), Y(i)) representing the variation in intensity of said colour component in orthogonal directions X, Y across said display; processing means for determining a resultant colour component value V(i,j) for a pixel to be displayed at a location (i,j) in said display in accordance with the following formula:   V(i,j)=f[a(X(i)b(Y(j))+c(X(i)d(Y(j))]     where the pixel has coordinates i,j and k is a normalizing constant, and where a, c, are functions of X(i), b, d are functions of Y(j) and f is an output function, said functions being chosen such that V(i,j) exhibits no discontinuities for all values of X(i), Y(j); and display means, responsive to said resultant colour component values V(i,j) for displaying a corresponding colour at a position in said display corresponding to that pixel.   
     
     
       2. Apparatus according to claim, 1, wherein said formula is chosen from:   V(i,j)=X(i)Y(j)/k     and     V(i,j)=[kX(i)+kY(j)-X(i)Y(j)]/k     
     
     
       3. Apparatus according to claim 1, wherein said processing means comprises a suitably programmed computer. 
     
     
       4. Apparatus according to claim 1, wherein said processing means comprises first, second, third and fourth look-up tables defining said respective functions a(Xi), b(Xi), c(Xi), and d(Xi); two multipliers to which outputs from said first and third look-up tables and said second and fourth look-up tables are fed respectively; and an adder for adding the outputs from said multipliers. 
     
     
       5. Apparatus according to claim 4, further comprising means for adding a random variation to the output from said adder. 
     
     
       6. Apparatus according to claim 4, further comprising a normaliser for normalising the output from said adder. 
     
     
       7. Apparatus according to claim 5, further comprising a normaliser for normalising the output from said adder.